GK Seminars SS 16
Tue 19.04.2016, 16.30 h
U. Kraus (Hildesheim)
Visualization of Special and General Relativity
Visualizations that adopt a first-person point of view are used to simulate the observation of relativistic scenes. This talk presents examples that include watching objects move at nearly the speed of light, being a high-speed observer looking at a static environment and having a look-around near a black hole.
Tue 03.05.2016, 16.30 h
B. Dönigus (Frankfurt)
Production of (anti-)matter and exotics at the LHC
The high collision energies reached at the LHC lead to significant production rates of light (anti-)(hyper-)nuclei in proton-proton, proton-lead and, in particular, lead-lead collisions. The excellent particle identification capabilities of the ALICE apparatus, based on the specific energy loss in the time projection chamber and the velocity
information from the time-of-flight detector, allow for the detection of these (anti-)nuclei. Furthermore, the high tracking resolution provided by the inner tracking system enables the separation of primary nuclei from those coming from the decay of heavier systems. This allows for the reconstruction of decays such as the hypertriton (a bound state of a proton, a neutron and a Λ hyperon) mesonic weak decay ( 3H -> 3He + π - ), the decay of a hypothetical bound state of a Λ with a neutron into a deuteron and pion or the H-dibaryon (a hexaquark state consisting of uuddss, respectively a ΛΛ bound state) decaying into a Λ, a proton and a π - . Results on the production of stable nuclei and anti-nuclei in lead-lead and lighter collision systems will be presented. Hypertriton production rates in Pb-Pb will also be shown, together with upper limits estimated on the production of hypothetical exotica candidates. The results will be compared with predictions for the production in thermal (statistical) and coalescence models.
Tue 10.05.2016, 16.30 h
A. Nelles (Irvine)
ARIANNA: Radio detection of high energy neutrinos on the Ross Ice Shelf of Antarctica
Detecting cosmogenic neutrinos (10^17 eV and above) will require detectors that are even larger than those in operation today. The ARIANNA project explores the feasibility of installing antennas on the surface of the Ross Ice Shelf in Antartica to detect the radio emission of neutrino induced showers in the ice. ARIANNA combines the advantage of the long attenuation length of the radio signal in ice with a low-cost instrumentation of a large volume to obtain a high sensitivity for neutrinos. In 2014 a hexagonal array has been completed and more than a year of experience in operation has been gathered. After covering some theoretical aspects of the radio emission of particle showers, I will focus on recent experimental efforts in the radio detection of neutrinos, with a special emphasis on ARIANNA. I will also cover the link to observations of cosmic rays through the radio emission of air showers and how this background has to be considered for neutrinos detectors.
Tue 24.05.2016, 16.30 h
R. Harlander (RWTH)
Some topics on Higgs physics
We will review some of the history, basics, as well as topical and philosophical issues in Higgs physics.
Tue 14.06.2016, 16.00 h
D. Blas (CERN)
On perturbative techniques to study structure formation in cosmology
The distribution of mass at cosmological scales contains a wealth of information about the fundamental constituents of the universe and their dynamical evolution. The exploitation of the current and forthcoming (high-quality) data requires methods to derive this ‘large scale structure’ in efficient and reliable ways and for different scenarios. In this talk I’ll summarise the attempts related to the largest scales, where the distribution of matter and its evolution can be described with fluid equations. I’ll comment on the ‘traditional’ approaches (Standard Perturbation Theory) and also on more recent progress (Effective Field Theory, Time-Slicing Perturbation Theory). If time permits I’ll discuss how the non-trivial dynamics of the BAO can be dealt with.
Tue 21.06.2016, 16.30 h
C. Hahnhart (FZ Jülich)
How can we unravel the mysteries of the QCD spectrum?
In recent years many states - including mesons in the charmonium and in the bottomonium sector as well as baryons in the charm sector - were observed experimentally that do not fit at all into the standard quark model picture. This is especially true for the charged bottomonia $Z_b(10610)$ and $Z_b(10650)$, the charged charmonia $Z(4430)$, $Z_c(3900)$ and $Z_c(4020)$ and the pentaquarks. The nature of these states is heavily discussed in the literature. The most prominent proposals put forward to explain the experimental signatures are compact multi-quarks (bound states of diquarks/anit-diquarks and eventually a quark), hadroquarkonia (denoting a compact heavy core surrounded by a light quark cloud), hadronic molecules (bound states of two color neutral hadrons) or signatures of certain singularities in the two-hadron interaction. A deeper understanding of those states should provide us with valuable insights into the inner workings of QCD at low energies. In this talk I will compare the different scenarios and explain, how it is possible to decide experimentally, which one of them is realized in nature.
Tue 28.06.2016, 16.30 h
J. Butterworth (University College London)
Measurements and Model Independence at Colliders
I will discuss how measurements can be defined and made at colliders, especially the LHC, to minimise the built-in theoretical assumptions. I will illustrate some potential problems, and give an example of using measurements.
Tue 05.07.2016, 16.30 h
M. Cirelli (Paris-Saclay)
Antinuclei production from DM annihilation
The annihilations of Dark Matter particles in the Galaxy can produce fluxes of antimatter, in particular antiprotons, antideuterons and possibly even nuclei of anti-helium. Since the astrophysical yield of these same species is rather well under control, the detection of an anomaly in these channels will constitute a clear signature for Dark Matter. I will discuss the mechanisms of production of antinuclei from DM, their propagation in the Galaxy and the detection strategies. I will pay some special attention to the antiproton data recently released by AMS-02, discussing which conclusions can be drawn and which ones can not (and should not) be drawn.
Tue 12.07.2016, 16.30 h
S. Sibiryakov (CERN)
Black hole physics: Gravity meets information theory
Black hole information paradox has stood as a challenge for theoretical physicists for over 40 years and the attempts to resolve it have revealed intimate connection between gravity and the theory of quantum information. I will review the notions of black hole entropy and Hawking radiation that are at the origin of the paradox, the existing approaches to resolve it, as well as its modern incarnation known under the name of the "firewall proposal". In the last part of the talk I will emphasize the need for a dynamical framework encompassing black hole formation and evaporation as a single quantum-mechanical process.
Tue 19.07.2016, 16.30 h
A. Lindner (DESY)
Illuminating the dark side: new approaches to search for the dominating matter in our universe
Elementary particle physics, our understanding of nature at smallest scales, and our knowledge on cosmology have joined forces to describe the development of the universe with great accuracy. This stunning success however predicts that the so-called dark matter responsible for the formation of structures in the universe. It should outbalance the forms of matter we know already by more than a factor five.
Recently, so-called weakly interacting slim particles, with the axion being its most famous representative, as possible
constituents of the dark matter have caught increasing interest in theoretical and experimental physics. Frequently such experiments are based on dedicated light sources and extremely sensitive light detectors. The seminar will focus on these investigations trying to bring the nature of dark matter to light.